Aggregate Demo

Aggregate 1

This example provides the function with a vector of numeric values, penguins$flipper_length_mm and a factor, penguins$species.

require(palmerpenguins)

aggregate(
  x = penguins$flipper_length_mm, 
  by = list(penguins$species), 
  FUN = mean, na.rm = TRUE)

NA

Aggregate Method 2

In this example, I’m using the formula notation:

aggregate(
  formula = flipper_length_mm ~ species, 
  data = penguins,
  FUN = mean, na.rm = TRUE)

NA

Boxplot with formula notation

The formula notation is handy for making conditional boxplots

boxplot(
  formula = flipper_length_mm ~ species, 
  data = penguins)

Aggregating by more than one factor

Here is how you can aggregate by species and sex:

aggregate(
  formula =  flipper_length_mm ~ species + sex, 
  data = penguins,
  FUN = mean, na.rm = TRUE)

Doubly conditional boxplot

The x-axis labels need help, but the box-and-whisker plots are now aggregated by species and sex.

boxplot(
  formula = flipper_length_mm ~ species + sex, 
  data = penguins)

Calculate critical t-values

n = nrow(penguins)

alpha = 0.05

qt(1 - alpha / 2, n - 1)

[1] 1.966904

qt(alpha/2, n - 1)

[1] -1.966904